Huimei Wang

Effects of Thidiazuron, basal medium and light quality on adventitious shoot regeneration from in vitro cultured stem of Populus alba×P. berolinensis

The effect of Thidiazuron (TDZ), basal media and light quality on adventitious shoot regeneration from in vitro cultured stem of Populus alba×P. berolinensis were determined to establish a high efficiency shoot regeneration system from stem explants of P. alba×P. berolinensis. Stems of Populus alba×P. berolinensis were collected from cultured shoots in vitro derived from dormancy buds of 3-year-old seedlings. The stem explants were cultured on MS medium containing 0.02-mg·L−1 NAA (naphthaleneacetic acid), and 0.1, 0.3, 0.5 and 1.0 mg·L−1 concentrations of TDZ to determine the effect of TDZ on shoot regeneration. Three basal media, i.e. MS, woody plant medium (WPM) and B5, were used to test their influences of different media on adventitious shoot regeneration. Green, red, blue and yellow plastic films in comparison with florescent light as control were used to observe their effects on shoot regeneration. The results showed that different concentrations of TDZ had an evident influence on shoot regeneration. Lower concentration of TDZ (0.1 mg·L−1) resulted in more adventitious shoot regeneration and higher concentration of TDZ (>0.1 mg·L−1) inhibited shoot regeneration. Among different media, MS medium exhibited a high efficiency for shoot regeneration, followed by WPM medium, while B5 medium inhibited shoot regeneration. Normal light and yellow light exhibited better effects on shoot regeneration, compared with other light.

Temporal changes of soil physic‐chemical properties at different soil depths during larch afforestation by multivariate analysis of covariance

Soil physic-chemical properties differ at different depths; however, differences in afforestation-induced temporal changes at different soil depths are seldom reported. By examining 19 parameters, the temporal changes and their interactions with soil depth in a large chronosequence dataset (159 plots; 636 profiles; 2544 samples) of larch plantations were checked by multivariate analysis of covariance (MANCOVA). No linear temporal changes were found in 9 parameters (N, K, N:P, available forms of N, P, K and ratios of N: available N, P: available P and K: available K), while marked linear changes were found in the rest 10 parameters. Four of them showed divergent temporal changes between surface and deep soils. At surface soils, changing rates were 262.1 g·kg−1·year−1 for SOM, 438.9 mg·g−1·year−1 for C:P, 5.3 mg·g−1·year−1 for C:K, and −3.23 mg·cm−3·year−1 for bulk density, while contrary tendencies were found in deeper soils. These divergences resulted in much moderated or no changes in the overall 80-cm soil profile. The other six parameters showed significant temporal changes for overall 0–80-cm soil profile (P: −4.10 mg·kg−1·year−1; pH: −0.0061 unit·year−1; C:N: 167.1 mg·g−1·year−1; K:P: 371.5 mg·g−1 year−1; N:K: −0.242 mg·g−1·year−1; EC: 0.169 μS·cm−1·year−1), but without significant differences at different soil depths (P > 0.05). Our findings highlight the importance of deep soils in studying physic-chemical changes of soil properties, and the temporal changes occurred in both surface and deep soils should be fully considered for forest management and soil nutrient balance.

Newly-formed photosynthates and the respiration rate of girdled stems of Korean pine (Pinus koraiensis Sieb. et Zucc.)

A stem-girdling experiment was carried out on an evergreen conifer, the Korean pine (Pinus koraiensis Sieb. et Zucc.), in mid summer in Northeast China. A 50 % higher respiration rate at the upper part of the stem was observed 3 d after stem girdling, and a stable higher rate (1.2–2.8 times) one week later. However, no higher soluble sugar or starch contents were found in the upper bark of the girdled stems in measurements over three weeks. These findings indicate that most of the newly-formed photosynthates were consumed by the high respiratory activity; this is also implied by the strong correlation between the photosynthetic photon flux over the canopy (PPF) and respiration at the upper parts of girdled stems. Moreover, the maximum PPF and cumulative PPF one day before measurement (PPFmax-Y and CPPF-Y, respectively) were closely correlated with the respiratory difference between the upper and the lower parts, but no such correlation was found with the instantaneous PPF (PPF-I) and cumulative PPF on the current day from sunrise to measured time point (CPPF-C). This shows that photosynthates newly formed by canopy needles need at least one day for transportation in order to increase the stem respiration at tree breast height.

Ectomycorrhizal Influence on Particle Size, Surface Structure, Mineral Crystallinity, Functional Groups, and Elemental Composition of Soil Colloids from Different Soil Origins

Limited data are available on the ectomycorrhizae-induced changes in surface structure and composition of soil colloids, the most active portion in soil matrix, although such data may benefit the understanding of mycorrhizal-aided soil improvements. By using ectomycorrhizae (Gomphidius viscidus) and soil colloids from dark brown forest soil (a good loam) and saline-alkali soil (heavily degraded soil), we tried to approach the changes here. For the good loam either from the surface or deep soils, the fungus treatment induced physical absorption of covering materials on colloid surface with nonsignificant increases in soil particle size (P > 0.05). These increased the amount of variable functional groups (O–H stretching and bending, C–H stretching, C=O stretching, etc.) by 3–26% and the crystallinity of variable soil minerals (kaolinite, hydromica, and quartz) by 40–300%. However, the fungus treatment of saline-alkali soil obviously differed from the dark brown forest soil. There were 12–35% decreases in most functional groups, 15–55% decreases in crystallinity of most soil minerals but general increases in their grain size, and significant increases in soil particle size (P < 0.05). These different responses sharply decreased element ratios (C : O, C : N, and C : Si) in soil colloids from saline-alkali soil, moving them close to those of the good loam of dark brown forest soil.

Establishment of Camptotheca acuminata regeneration from leaf explants

Plantlet regeneration through shoot formation from young leaf explant-derived callus of Camptotheca acuminata is described. Calli were obtained by placing leaf explants on Woody plant medium (WPM) supplemented with various concentrations of 6-benzyladenine (BA) and naphthaleneacetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D). Callus induction was observed in all media evaluated. On the shoot induction medium, the callus induced on the WPM medium containing 19.8 μM BA and 5.8 μM NAA was the most effective, providing high shoot regeneration frequency (70.3 %) as well as the highest number of shoots (11.2 shoots explant−1). The good rooting percentage and root quality (98 %, 5.9 roots shoot−1) were achieved on WPM medium supplemented with 9.6 μM indole-3-butyric acid (IBA). 96 % of the in vitro rooted plantlets with well developed shoots and roots survived transfer to soil.

Spatial Variations in Concentration, Compositions of Glomalin Related Soil Protein in Poplar Plantations in Northeastern China, and Possible Relations with Soil Physicochemical Properties

Concentration of Glomalin Related Soil Protein is reportedly close related to soil functions, but few data is available for GRSP compositional variations and function related to soil properties. In this paper, soils from 0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm, and 80–100 cm layers were collected in 72 poplar shelterbelts in Songnen Plain (6 regions) for implementing this data shortage. GRSP mainly consists of stretching of O–H, N–H, C–H, C=O, COO–, C–O, and Si–O–Si and bending of C–H and O–H. It has seven fluorescent substances of tyrosine-like protein, tryptophan-like protein, fulvic acid-like, humic acid-like, soluble microbial byproduct-like, nitrobenzoxadiazole-like, and calcofluor white-like, with characteristic X-ray diffraction peak at 2θ = 19.8° and 129.3 nm grain size as well as 1.08% low crystallinity. Large spatial variations (intersite and intrasite down profile) were found in either GRSP concentration or these compositional traits. Regression analysis clearly manifested that soil pH should be responsible for these variations. However, negative relations between soil bulk density and GRSP quantity were observed, but not its compositional traits. These basic data in poplar shelterbelt forests are good for understanding the underlying mechanism of GRSP in soil functional maintenance.

Effect of inland salt-alkaline stress on C4 enzymes, pigments, antioxidant enzymes, and photosynthesis in leaf, bark, and branch chlorenchyma of poplars

The effects of soil salt-alkaline (SA) stress on leaf physiological processes are well studied in the laboratory, but less is known about their effect on leaf, bark and branch chlorenchyma and no reports exist on their effect on C4 enzymes in field conditions. Our results demonstrated that activities of C4 enzymes, such as phospholenolpyruvate carboxylase (PEPC), NADP-malic enzyme (NADP-ME), pyruvate orthophosphate dikinase (PPDK), and NADP-dependent malate dehydrogenase (NADP-MDH), could also be regulated by soil salinity/alkalinity in poplar (Populus alba × P. berolinensis) trees, similarly as the already documented changes in activities of antioxidative enzymes, such as superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR), pigment composition, photosynthesis, and respiration. However, compared with 50–90% changes in a leaf and young branch chlorenchyma, much smaller changes in malondialdehyde (MDA), antioxidative enzymes, and C4 enzymatic activities were observed in bark chlorenchyma, showing that the effect of soil salinity/alkalinity on enzymatic activities was organ-dependent. This suggests that C4 enzymatic ratios between nonleaf chlorenchyma and leaf (the commonly used parameter to discern the operation of the C4 photosynthetic pathway in nonleaf chlorenchyma), were dependent on SA stress. Moreover, much smaller enhancement of these ratios was seen in an improved soil contrary to SA soil, when the fresh mass (FM) was used as the unit compared with a calculation on a chlorophyll (Chl) unit. An identification of the C4 photosynthesis pathway via C4 enzyme difference between chlorenchyma and leaf should take this environmental regulation and unit-based difference into account.

Differences in the activities of eight enzymes from ten soil fungi and their possible influences on the surface structure, functional groups, and element composition of soil colloids.

How soil fungi function in soil carbon and nutrient cycling is not well understood by using fungal enzymatic differences and their interactions with soil colloids. Eight extracellular enzymes, EEAs (chitinase, carboxymethyl cellulase, β-glucosidase, protease, acid phosphatase, polyphenol oxidase, laccase, and guaiacol oxidase) secreted by ten fungi were compared, and then the fungi that showed low and high enzymatic activity were co-cultured with soil colloids for the purpose of finding fungi-soil interactions. Some fungi (Gomphidius rutilus, Russula integra, Pholiota adiposa, and Geastrum mammosum) secreted 3–4 enzymes with weak activities, while others (Cyathus striatus, Suillus granulate, Phallus impudicus, Collybia dryophila, Agaricus sylvicola, and Lactarius deliciosus) could secret over 5 enzymes with high activities. The differences in these fungi contributed to the alterations of functional groups (stretching bands of O-H, N-H, C-H, C = O, COO- decreased by 11–60%, while P = O, C-O stretching, O-H bending and Si-O-Si stretching increased 9–22%), surface appearance (disappearance of adhesive organic materials), and elemental compositions (11–49% decreases in C1s) in soil colloids. Moreover, more evident changes were generally in high enzymatic fungi (C. striatus) compared with low enzymatic fungi (G. rutilus). Our findings indicate that inter-fungi differences in EEA types and activities might be responsible for physical and chemical changes in soil colloids (the most active component of soil matrix), highlighting the important roles of soil fungi in soil nutrient cycling and functional maintenance.

Influence of Long-Term Thinning on the Biomass Carbon and Soil Respiration in a Larch (Larix gmelinii) Forest in Northeastern China

Thinning management is used to improve timber production, but only a few data are available on how it influences ecosystem C sink capacity. This study aims to clarify the effects of thinning on C sinks of larch plantations, the most widespread forests in Northeastern China. Both C influx from biomass production and C efflux from each soil respiration component and its temperature sensitivity were determined for scaling-up ecosystem C sink estimation: microbial composition is measured for clarifying mechanism for respiratory changes from thinning treatment. Thinning management induced 6.23 mol C m−2 yr−1 increase in biomass C, while the decrease in heterotrophic respiration (R h) at the thinned sites (0.9 mol C m−2 yr−1) has enhanced 14% of this biomass C increase. This decrease in R h was a sum of the 42% decrease (4.1 mol C m−2 yr−1) in litter respiration and 3.2 mol C m−2 yr−1 more CO2 efflux from mineral soil in thinned sites compared with unthinned control. Increases in temperature, temperature sensitivity, alteration of litters, and microbial composition may be responsible for the contrary changes in R h from mineral soil and litter respiration, respectively. These findings manifested that thinning management of larch plantations could enhance biomass accumulation and decrease respiratory efflux from soil, which resulted in the effectiveness improvement in sequestrating C in forest ecosystems.

Light-sensitive features of seed germination in the invasive species Ageratina adenophora (syn. Eupatorium adenophorum) in China

Ageratina adenophora (Crofton weed) is a noxious invasive plant in several countries and its germination features favor its invasiveness. The aim of this study was to characterize the light-sensitive seed germination of this weed. Two to five-fold higher germination was observed under light conditions than under dark conditions. Dormancy-breaking methods of low temperature pre-treatment, pre-soaking with KNO3 solution, polyethylene glycol, and salicylic acid did not influence germination under either light or dark conditions. Very low light (39 μmol·m -2 ·s -1 , 25% light transmittance) tripled seed germination from 22.3 to 66.7%, when compared to no light. Germination under violet, blue and green glass papers was significantly lower than that under yellow, orange, and red ones. Significant correlations between red-light intensity, red/far-red ratio and germination indicated that these 2 types of light may be responsible for the germination differences. Experiments under narrow band filters also proved this; red light at 630 nm could induce germination, while far-red light 740 nm could prevent germination. Thus, red/far-red light was effective in the photoblastic germination of Crofton weed, while other treatments could not replace light during germination. This photoblastic germination could favor the fast colonization of this weed when the seeds in deep soil approach the surface.